1. Field of the Invention
The present invention relates to a switching power supply apparatus including a voltage step-up converter.
2. Description of the Related Art
In a case of a power supply apparatus that receives power from a commercial power supply and that has high power capacity, a voltage step-up converter for power factor correction (PFC) is practically required to be mounted in order to clear harmonic current regulation. In a case of a power supply apparatus that receives renewable energy, such as sunlight, since input voltage is greatly varied, a power supply apparatus including a voltage step-up converter in its front stage may be configured in order to correct the variation. When such a power supply apparatus including the voltage step-up converter is configured, the voltage step-up converter is controlled so that the voltage step-up converter detects output voltage and compares the output voltage with reference voltage to make the difference between the output voltage and the reference voltage equal to zero in order to output constant voltage. However, an error (deviation) occurs in the output voltage due to, for example, the resistance in wiring or the variation in the reference voltage. Since selection of components or designing of a circuit with a margin for error causes problems including an increase in size of the apparatus, an increase in cost, and a reduction in efficiency, it is necessary to perform correction in order to obtain an output voltage with higher accuracy. Accordingly, Japanese Unexamined Patent Application Publication No. 2009-240063 discloses a technology to suppress the deviation in the output voltage caused by the variation in a reference voltage source or the variation in a resistor voltage divider in a constant-voltage power supply apparatus.
However, since a measuring terminal for externally measuring the voltage is not generally provided in a circuit path, it is not possible to directly measure the output voltage (intermediate bus voltage) of the voltage step-up converter in the case of the power supply apparatus including the voltage step-up converter in its input state. Accordingly, it is not possible to perform a process in which the intermediate bus voltage that is detected with a detection circuit is compared with the intermediate bus voltage that is directly measured to correct the result of the detection of the intermediate bus voltage including the error. As a result, there is a problem in that it is not possible to set the intermediate bus voltage to a certain value not to accurately output the constant voltage from the voltage step-up converter. This problem is not resolved with the technology disclosed in Japanese Unexamined Patent Application Publication NO. 2009-240063.